The ability to compare objects according to discrete dimensions such as size, color or shape seems basic to human intelligence. However, developmental research indicates that knowledge of dimensions is complex and emerges gradually throughout the preschool and early school years. This research investigates a componential model in which an understanding of identity, wholistic similarity, attribute, dimension, direction, intensive order, and continuity comprises the structural core of dimensional knowledge. The proposed project tests the developmental independence of these components and their order of acquisition. Performance in verbal and nonverbal tasks will be compared to provide a complete description of the development of dimensional concepts. Certain aspects of this growth may reflect experience with objects, other aspects may reflect experience with language. Children aged 2-8 will be the primary participants. The experiments compare children's conceptual knowledge of relations and their acquisitions of the words that refer to relations. Conceptual knowledge will be assessed in an imitation task that requires abstract inferences about relations. Word knowledge will be measured by verbally asking children to select objects specified by attribute or relation, e.g. "Find the big one", "Which two are the same." Additional experiments investigate the perception of relations in children and adults in order to understand the development of the mechanisms that underly the developmental growth in relational knowledge.